Manufacture of phosphoric acid



l. HECHENBLEIKNNER MANUFACTURE or PHOSDPHORIQ ACID Filed March 24, 1931 Feb. s, 1935.

liar/rue /54 INVENTOR \ngenuin Hechenb! 'kner 6 BY 7 g h ATTORNEYS Paenei ,1935,

UNITED STATES v PATENT OFFICE? it r 1,990,233 I Q i I a MANUFACTURE OF PHosPnoItIo ACID Ingenuin Hechenbleikner, Charlotte, N. C'., as-

s'ignor to Chemical Construction Corporation, Charlotte, N. 0., a corporation of Delaware Application March 24, 1931, Serial No. 524,793

4 Claims. (01. 23-165) This invention relates to phosphorous comto cool the combustion gas supplied thereto. pounds, particularly phosphoric acid, and to a This is best' accomplished by feeding the anmethod and means for manufacturing the same. hydride gas together with a spray of makeup Processes developed in recent years make .availwater to the absorber. The water spraycools able in large quantities elemental yellow phosthe combustion gases and preliminarily absorbs "'5 phorous obtained from mined phosphate rock. some of the anhydride." The remainderof the The phosphorous may be safely'shipped'in'large anhydride is absorbed as the gas is bubbled quantities in tank cars containing water prothrough the body of phosphoric acid in the tectively covering the same. The primary object absorber.

of the present invention is to provide a method It is convenient to be able to obtaincondensed i6 and means for manufacturing phosphoric acid acid in the coke filter which is of the same or phosphates directly from yellow phosphorous St eng a he i y of r in r made in an exceedingly rapid and economical manner. in the absorber. The efiiciency of the coke filter, In accordance with my process the phosphorous as Well s the Stre O a d e h er rj'm is molten and fed in a liquid state to a furnace f m d p d ot t nly un t cooling f the is in which it is burned to form the desired oxide filter, but also upon-thetemperature of the waste or acid anhydride. The oxide is then fed in a ases supplied th eto. n co danc w a vaporous state directly into an absorbing liquid, furth je t and f tu of y inv n these such as water or phosphoric acid if phosphoric Waste gases are cooled during their passage from acid is to be made, or alkali olutions-ii alkaline the a r to t filter, preferably by f in 20' phosphate solution re t b ad the same through a, small additional water spray The anhydride gasis readilytaken'up in this h a O flow o Which be pp pri y manner. However, some of the acid in vaporous j d toeregulete the Strength of a d bta n d or mist form may be carried along with the waste from the filter- '25 gases discharged irornfth'e absorber. This con the eecoihpliehment 0f the foregeing he dition is aggravated by, the fact that the hydrah, other s; Ias Wi e t appea tion of the anhydride" is exothermic and tends y i v o QOh S in the method d- 91 11 5 to increase the temperature of the waste gases tllS elemen i their Ieletieh One tethe Oth leaving the absorber. AcCordingIyJa'further obxas e n r, are e a ticul r described ject of the present invention is to regain any i t pec t a SQ g to b defined in 30 acid contained in the waste gases, and thereby thefeleims- The Specification vis!Vaecoihpehied increase the over-all efficiency of the apparatus. by aw in W c q With this object in view the waste 'gasesdis 1 is a plan View of apparatus: cone charged from the absorber are cooled and prefstructed in accordance with the present; inf 35 erably also obstructed'as by passing the same vention; and 35 through a cooled multiple baffle system in order Fig. 2 8a p i lly i n d side elevation to condense residual acid contained in the waste of thefsarne. H p a I w gases. The multiple bafile preferablytakes the Referring to the drawing, the apparatusjcomg form of a coke filter throughwhich the waste prises generally a phosphorous tank A, aphos- 40 gases may be passed upwardly. The filter may phorous furnace B, an absorber C, a coke filter 4'0 be water cooled or, more;simply provided with D, and acid tanksE for receiving the product a lead roof for air cooling. Acid condensed in acid.

the coke filter flows downwardly in intimate'con- Considering the apparatus in greater detaihthe tact with the rising gases, and finally is collected ph sp o a A18 p ferably buried, as shown, i

at the bottom of the filter. and is filled with a body of phosphorousal'zr The anhydride is preferably absorbed in phoswhich is protectively covered by a body of water phoric acid, and this is withdrawn from the l4. The tank includes a heating coil 16 sub;- absorber when of desired strength, the deficiency merged in the bodyv of phosphorous 12. A heating being made up by the addition of makeup water. medium, such as hot water or steam, is supplied a V The products of combustion fromthe furnace tocoil 16. vIn the present case steam isusedand 59 are atatemperature which is considerably higher is supplied to. the coil from a boiler lfilthrough than the optimum'temperature for rapid absorpa pipe 20, ,whilefthe discharge end of coil' 16 is tion. Further objects of the present invention provided with an appropriate steam trap22. In

5 are to provide thedesired makeup water'for the asmuch as the phosphorous melts at'a relatively 1.;-

operation of the absorber, and at the "same time low'temperature, approximately 112 Fahrenheit,

keeping the same molten andsafely covered-with the body of water 14 presents no difiiculty.

The molten phosphorous is pumped from the tank Aby a pump 24, and fed to the furnace B.

The phosphorous piping is preferably .made as short and as direct as possible, and is jacketed as shown at 26 to prevent solidification of the phosphorous and stoppage of the feed l ne.

Air is supplied to the furnace by an appropriate blower 28. The rate of airsupply is made amply sufiicient to insure thorough combustion ofthephosphorous.

The furnace B preferably comprises a asteel shell which is fitted with a'fire resistant lining.

More specifically, the shell may be lined with asbestos paper, insulating brick,-and then fire brick, the whole forming a composite'lining'in dicated generally at 30. The furnaceyis, also provided with bafile walls 32 which lengthen the path and time of the combustion gases'in the furnace and insure intimatemixture of the same, thereby permitting efficientand complete combustion'of the phosphorous. I

' Theburning of the phosphorousmaybe accomplished in any desired manner. In the presen'tic'ase the phosphorous is simply discharged from a pipe 34 onto the nearer the furnace near the inlet end of the same, where it is instantaneously ignited and burned by the stream of air beingblown into the-furnace through duct 36. The burning mechanism not shown in detail, but may take any of the forms described in my copending application, Ser. ,No. 524,794,

. filed on even date herewith, or, if desired, may

take the .form of t a preferably jacketed spray burner or gun such as is disclosed in my copend- 'ing-applicatiom'ser. No. 321,115, filed November 22,1928. The particular way in which the phosphorous is ignited is of no' directimportance as regards the present invention which deals with the complete process for the production of phosphoricacid. r

The absorber C takes the form of apreferably horizontally disposed drum which is" approximately half filled with a body 40 of phosphoric acid. The drum comprises a steel shell lined with acid resistant: material. Specifically, the lining may comprise a layer'ofasbestos followed by a layer of lead and finally a surface ofacid-proofbrick The furnaceB and absorber C may beclosely juxtaposed, thereby. shortening and simplifying the piping between the same, which'includes merely an outlet42 from furnace B, and inlet 44 to absorber C, and a flanged connection 46 therebetween. This piping may also be ap-,

propriately-lined to resist temperature and acid. The inlet 44 of the absorber preferably includes a downwardly extending tube 48 the lower-end of v T which is immersed in the body of absorbing liquid 40'. ,This'tube is preferably made of carbon so as to be acid resistant, and its immersion in phosphoric acid insures discharge of the combustion gases through the acid.

Product acidof desired concentration is withdrawn from the bottom of absorber C through a pipe50 and led to atank 52. The tank may be lined with lead and acid-proof brick, and is preferably buried, thereby permitting of simple gravpity fiow of the product acid. The piping is pref moved from'absorber C in batches under manual erably made of duriron. The acid may be recontrol, or a steady leakage or trickle may be preferred In either case the flow may be regulated by valve 54. The level of the liquid in absorber C is maintained by feeding. makeup the same value.-

liquid, preferably water, into the absorber. In the present case this water is supplied through a pipe 56 which terminates in a small spray head 58 located within the carbon tube 48. The rate of flow of makeup water maybe regulated by a valve 60. The resulting spray of water when applied in this manner serves a dual function'in that it cools the combustion gases entering the absorber,

and preliminarily absorbs anhydride from the same, as Well. as makes up for the product acid withdrawn from the absorber.

The waste gases from absorber C are fed.

through outlet 62 interconnecting pipe 66, and

inlet 68 to the bottom of the'coke filter D. The gases then rise upwardly through the coke which 'baflle which physically obstructs the flow of the gas and more. particularly. of liquid or mist carried thereby. The roof of the filter is being continually air cooled, and this aids condensation of any acid contained'in the waste gases. densed acid flows downwardly through the filter and is collected at the bottom of the same and" run through a discharge pipe '70'to acid tank "'72.

During its descent in the filter the condensed acid 5 helps regain additional acid from the Waste gases rising throughthe filter. The clean waste gases.

are finally discharged through outlet 74; v I

.The hydration of the anhydride in absorber C is exothermic, and the resulting evolution of heat causes an unexpectedly high acid-contentin the waste gases discharged from the absorber. -Despite thisfact, the present apparatus, including cooling and baffling condenser means such as the coke filter D heretoforedescribedinay readily be operated with an acid yield'of as highas-'99 In other words, there is no appreciable loss of phosphoric acid in the absorption system comprising absorber C and coke filter D operating in combination. I j q If desired, an additional water spraysupplied with water through a pipe and valve82 may be provided in :outlet 62 of the absorber C. This spray cools the waste gasesgoing to the r'coke' filter, and makes-it possible to regulate the r strength of theIacid-,collected therein. In this wayv the strengths of the phosphoric acid colctedin tanks 52 and-72 may be adjusted to The process is exceedingly efficient in commercialpractice and requires only relatively'co'mpact 'apparatusfor practicing the same. The power consumption for operating the phosphorous pump and air blower isrelatively, small. Five hundred to six hundred pounds of phosphorous may be burned per hour in a plant of moderate (Baum) acid. 7

. size producing a high and efilcient yield of 55 detail in connectionwith the direct production of phosphoric acid, it will be understood that the process may equally'well be applied to the While the process has been described in some.

.1 acts in effect merely as a complicated multiple. 7

Such conproduction of phosphorous salts. For example,

\ an absorber may beused in which alkali solutions The phosform the acid anhydride.

oughly recapture from the same the desired product. The efiiciency of the system as a whole may be increased by supplying makeup water in the form of a cooling spray in the passage of the combustion gases to the absorber, while an additional spray may, if desired, be employed at the outlet from the absorber.

It will be apparent that while I have shown and described my invention in the preferred form, many changes and modifications may be made in the method and structure disclosed, without departing from the spirit of the invention, defined in the following claims.

I claim:

1. A method of producing phosphoric acid solu tion which comprises forming phosphoric anhydride in the vapor state, mixing said vapors with a spray of water, causing the mixture to pass through a body of an aqueous solution of phosphoric acid to cause absorption thereof, and finally cooling the gases,

2. A method of producing phosphoric acid solution which comprises forming phosphoric .anhydride in the vapor state, mixing said vapors with a spray of water, causing the mixture to pass through a body of an aqueous solution of phosphoric acid to cause absorption thereof, and finally cooling the gases by passing the same through a cooled bafile' means.

3. A method of producing phosphoric acidsolution which comprises forming phosphoric anhydride in the vapor state,'mixing said vapors with a spray of water, causing the mixture to pass through a body of an aqueous solution of phosphoric acid to cause absorption thereof, finally cooling the gases by passing the same through a cooled bafile means and collecting the condensed "acid from said means. 

